Prerequisites for dynamic spectrum access

Heikki Kokkinen |V Sridhar | Updated on: Jul 03, 2022
Spectrum sharing

Spectrum sharing | Photo Credit: Andrey Suslov

An important regulatory initiative would be to set up a country-wide geospatial spectrum database

Radio spectrum for commercial mobile services continues to be scarce. Countries around the world have recognised the importance of efficient utilisation of this scarce resource and have initiated regulatory and policy steps towards flexible approaches to spectrum management, including sharing of licensed spectrum, and releasing unlicensed spectrum for mobile services.

Technologies for shared access and the associated standardisation activities have also progressed towards possible large scale deployments. Realising these trends, in a welcome move, the Telecom Regulatory Authority of India (TRAI) is expected to start the consultation process to share spectrum dynamically. The static spectrum sharing guidelines were released by the Department of Telecommunications way back in 2015 and are being practiced by the Mobile Network Operators (MNOs).

Dynamic spectrum access enables radio spectrum to be shared by two or more entities (e.g. MNOs, TV broadcasting stations, enterprises deploying captive non-public networks) across the space and time domain.

Spectrum sharing methods

The widely used spectrum sharing licensing methods are: (i) Licensed Shared Access (LSA) being deployed in Europe; and (ii) Spectrum Access System (SAS) widely being deployed in the US.

The European Commission released guidelines for LSA in February 2014. LSA is a complementary spectrum management tool that facilitates the introduction of new users in a frequency band while maintaining incumbents’ existing services in the same band. LSA ensures protection against harmful interference for the incumbents and a certain level of guarantee in terms of spectrum access for the LSA licensees.

In April 2013, Finland was the first country to trial the LSA on 2.3 GHz band, where the incumbents — Program Making Special Events (PMSE) licensees that use professional wireless camera links of the broadcasting and TV production companies, share their spectrum on a dynamic basis with the mobile operators. LSA is incorporated in the regular process of the Radiocommunications Agency Netherlands. It is compulsory for the PMSE sector to use the LSA booking system in the 2.3-2.4 GHz band.

This obligation is incorporated in the licenses of PMSE users in this band. Also, the National Regulatory Authorities (NRA) of Italy, France, Russia and Portugal have piloted LSA. The spectrum sharing in these cases has either allowed the MNOs to increase their public network capacity or enterprises to deploy Captive Non-Public 5G Networks.

Federal Communications Commission (FCC) proposed the release of 150 MHz in 3550-3650 MHz (3.5 GHz Band) being used for military and satellite communication for shared use in 2012.

In line with the recommendations of President’s Council of Advisors on Science and Technology (PCAST), Citizens Broadband Radio Service (CBRS) includes three tiers of service users: (i) Incumbent, (ii) Priority Access License (PAL), and (iii) General Authorized Access (GAA). PAL and GAA tiers allow access for users with automatic authorization to deploy a wide range of services.

The CBRS band is suited for Fixed Wireless Access, public 5G and also for captive use. CBRS deploys a SAS to assign and an Environmental Sensing Capability (ESC) to monitor spectrum use and associated interference, thereby protecting higher priority users from the interference of the lower priority users. A GAA tier is assigned on an opportunistic and non-interfering basis within designated geographic areas.

Sharing of spectrum under appropriate regulatory structure between MNOs and other spectrum users is possible in the unlicensed commons spectrum as well. One such example is the coexistence of the 4G-Long Term Evolution (LTE) technology being deployed by the mobile operators with Wi-Fi providers in the 5 GHz band. Additionally, within the public mobile networks, MNOs may deploy Dynamic Spectrum Sharing (DSS) to ensure gradual migration from 4G-LTE to 5G.

Whatever may be the methodology that we choose, an important regulatory initiative at this stage would be to set up a country-wide geospatial spectrum database that contains the spectrum in use across different areas by the various operators.

Without this first step, the dynamic spectrum access methods will not take off in the country. As researchers, we have often found it very difficult to get the data on the frequencies allocated to the operators in different bands across the License Service Areas.

However, spectrum sharing requires the micro level data on spectrum in use by the operators. It is time that TRAI initiates the development of such data base soon to kick-start the process.

Sridhar is Professor, IIIT Bangalore; and Kokkinen, CEO, Fairspectrum, Finland. Views expressed are personal

Published on July 03, 2022
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